Method of making lens blanks



April 10, 1945. P, OHNSTON 2,373,246

METHOD OF MAKING LENS BLANK Original Filed March 21, 1941 3 Sheets-Sheet 1 paws/31L April 10, 1945. JOHNSTON 2,373,246

METHOD OF MAKING LENS BLANK Original File d March 21, 1941 s Sheets-Sheet 2 7 7X 75 3mm 50 PERRY Q/OHAASTO/V X 6/ v v I 7/ (962M? L Patented Apr. 10, 1945 Mani Fries 12,373,246 METHOD OF MAKING LENSBLANKS Perry J ohnstonjFord City, Pa., assignorto PittsburghPlate Glass Company, Allegheny County, "Pa, a corporation of Pennsylvania 1 Original application -March -21, .1941, SrialNo. 384,518. Divided and this application January 2 Claims.

This invention relates'to ;-methods of molding lens blanks and it has particular relation .to the formation of compound or composite lens.

This application-is a division of my .copending' application, Serial .No. 384,518, filed March 21, 1941, now Patent .No. 2,335,419, granted .Nov. 30, 1943.

One .object of the inventionis to provide an improved method of making a .lens blank in which two or more sections'of glass are incorporated.

Another object ofthe'invention is to provide an improved .methodof molding and assemblinga composite lens blank.

Another object of the invention is to provide an improved apparatus. for molding lens zblanks. Another object of the invention is toprovi'de 1,. 1942, Serial. No. 425,294

an improved method of'making relatively'ismall v strains in the small blank. Thereis'alsmdifficulty in molding these blanks in such manner asto perfect absolutely perpendicular relation between the faces of the blank and their adjacent edges.

It is desirable to mold theselenses originally with perfectly squared edges because otherwise the line of demarcation between the sections willbe visible and objectionable after completion of the.

article. On the other-handit has heretofore been difficult to remove'molded glass froma mold if the walls thereof are notat-least sloping to a slight degree.

This invention isdesigned t0=obviat the difficulties previously encountered under these .:circumstances byproviding for the manufacture of sections of composite lenses so that their faces and edges are perfectly squaredand at thesame time providing for the manufacture of the smaller sections which will .be substantially free from strains or other undesirable characteristics.

In the drawings: I Fig. 1 is a verticalsection of a molding apparatus inv which the invention 'has been .inco'x- Jporated; ,Fig. 2 is a plan of a composite lens blank; Fig. ,3 isa cross section .of a blank taken substantially along the line'IIIIII of Fig. -2; Fig. 4..is "a'fragmentary plan, on a larger scale of a molding apparatus; Fig.5 is a fragmentary vertical section of the molding apparatu taken substantially .along the .line V-AV of Fig. 4 and including in addition .a molding plunger positioned therein; Fig. -6 is .a fragmentary cross section taken substantially along the line VI-VI of Fig. 4; Fig. 7 .is a. fragmentary plan similar to Fig. 4 illustrating another formof moldin structure; .Fig. 8 is a cross section taken substantially alongthe line VIIIVIII ofjFig. 7,; Fig. 9. is a fragmentary. plan similar .to Fig. 4 of another form of moldingstructure; Fig. 10 is a vertical section on a larger scale .of themolding apparatusshown inFigLB and including inaddition a. plunger in .rnolding .positionpFig ll is a vertical section :similar to Fig. 10, but at right angles thereto and with the plunger retracted; Fig. l2 is a crosssection taken substantially along .theline XlL-XII of vFig. .11; and Fig. .13 is a plan of a composite .lens blank having wings formed in the apparatus shown in.Figs. 9 toll.

Referring-to Figs. 1 to 4, amold frame 20 is providedrigidlythereon with abed platefil upon which a mold seating anvil 23 is-secured bymeans of bolting elements 25. Theupper portion .of theframeis provided:rigidlythereon with-a cylinder 3i! whichhas connected at its oppositeends fluid supply pipes 3| 'andliii through .whichiiuid can 'be passed to operate a piston 3.5-slidable in the cylinder. A plunger 3'! rigidly secured to the piston constitutes a piston rod, and a guide 38 through which the, shank of theplunge'r slides is securedrigidly to the body of the frame and extends laterally therefrom.

The anvil 23 has a horizontal upper mold seat 40 horizontally leveled to precision and is formed-with upright walls 63 converging from the front portion of theseatrearwardlytoward the body of the frame. .A.sectional.mold 45 seats squarely upon the seat 4i) 'and'is provided with spaced end sections 4-; which are integral with and rise integrallyfrom the mold base it at opposite ends thereof. Opposite side'sections are slidable upon the upper surface of the-mold base 48 towardand away from opposite sides of the end sections 41, and these-side sections converge along their outer walls correspondingly to the converging character of .the anvil .walls 43 between which they are movable .to wedged position. Amold chamber .5l isthus formed. andits bottom-is horizontally'leveled to-precision. Up-

other upon the upper surface of the base.

right bolts 53 are threaded in the base 48 and extend upwardly through slots 54 formed in the side sections 50 to permit lateral sliding action of these sections toward and away from each The inner vertical side walls of the sections 50 are precisely squared with respect to the bottom of the molding chamber. In wedging the converging outer sides of the sections 55 between the walls 43, the inner sides of said sections adjacent their outer ends are abutted against opposite sides of the end sections 4-! to present the molding chamber 5| for the reception of the plunger 31. While the bottom of the molding chamber and each vertical wall portion are formed withv such precision as to be absolutely'squared, the chamber forming inner walls of the end sections 4! can be formed to converge slightly from top to bottom for the purpose of facilitating the removal of molded glass therefrom.

Compression springs 57 can be horizontally connected between corresponding end portions of the side sections 50 and the end sections are cut away (Fig. 6), as indicated at 58, to accommodate the compression springs which constantly exert force tending to spread the sections.

The mold containing a body of molten glass is placed flatly upon the upper surface of the anvil base 48 and then is wedged between the converging walls 43 thereof. In this position the molding chamber is alined vertically with the molding plunger 3'! which is operated downwardly to the position shown in Fig.5 to mold'the central lens, section 60. which, by virtue of the right angled relation between the bottom and sides of the mold chamber are so formed as to have perfectly squared edges 8!. Wingsections 53 having edges formed to the same shape as the edges 6| are fused to the latter edges to complete a composite lens unit '54 (Fig.2). A lens of this type is relatively small and the wing sections, must be carefully formed in order toavoid undesirable strains and to insure properconsistency of the composition required for use in lens manufacture.

A second molding apparatus 10 (Figs. '7 and 8) is designed to provide for the formation of the wing sections 63 and has the same general structure as that described with reference to Figs. 4 to 6, with the exception of differences in the mold chamber and plunger end. Accordingly corresponding reference characters are employed to indicate like portions of the apparatus, and the foregoing description of mechanical parts applies thereto.

In connection with this form of mold, it is desirable to produce double blanks H which have perfectly squared edges for abutting and fusing with the squared edges BI of the central blank 50. The bottom of the mold chamber 5| is provided with a knife edge 13 (Fig. 8) extending upwardly and integrally from the mold base Q8 and the bottom surface of theplunger 31 is also provided with the knife edge I5 which is adapted to assume the position indicated in Fig. 8 in parallel opposed relation to the knife edge 73. The outer sides of the blank sections 63 are thus molded precisely to squared relation and a neck 18 is formed centrally of the blank II which can be severed therealong after removal from the mold.

In molding smaller sections of lens blanks it may be diificult to cause the glass to fill out the diagonally opposite corners of the mold chamber, and for this reason the type of mold shown in Figs. 9 to 12 has been designed. In the form of structure shown in these figures, the mold chamber 5| does not have movable side sections and its inner molding wallsare slightly inclined or converged slightly in a downward direction for the purpose of facilitating removal of the molded glass therefrom. The knife edge 13 runs centrally and integrally with the chamber bottom and the plunger 31 is provided with complemental knife edge 15 whichis alined in parallel relation to the knife edge I3.

A small body, of optical glass which can be in block form is heated until it becomes softened or molten, but not suificiently fluid to flow materially without pressure being exerted thereon, and this body is placed in the mold chamber. After a body of molten glass has been placed in the mold chamber H and pressed by lowering the plunger 31, the knife. edges13 and I5 will have been brought close together in slightly spaced edge-to-edge relation to provide a double lens blank 86 having a relatively narrow neck 8| centrally dividing the blank into two sections corresponding to the sections 63 already described, with the exception that the neck portions of the blank sections are milled or ground off toform squared edges. These edges are fused to the central blank 54 in the manner previously described and as shown in Fig. 13. This type of arrangement avoids the use of a mold having movable side sections for manufacture of the smaller wing sections of the lens but it entails additional milling or grinding of the edges to squared relation.

It may be desirable under certain conditions to provide'additional structure to insure proper alinement of the knife edges 13 and 15 with each other and to this end, a finder 85 is secured transversely and 'adjustably through the plunger by means of a set screw 8'1. Opposite end portions of the finder are bent downwardly to form fingers 88' adapted to register with openings 89 provided in the upper portion of the mold.

Although practical structure involving the invention has been shown and described in detail,

it will be apparent to those skilled in the art that the invention is not so limited but that various changes can be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. A method of forming a lens unit which comprises melting a body of glass, molding under pressure from said body a central glass blank,

. forming opposite section-receiving edges on said blank, melting under pressure a body of molten glass into two sections integrally connected by a narrow central neck adapted to be broken without marring the two sections but sufficiently strong to insure unitary molding of the integrally connected sections, severing the latter body at its narrow neck to separate its two sections, finishing an edge of each of said sections after severance to fit in edge-to-edge relation on said central blank, and fusing the section-receiving edges to the finished edges of the lens sections to form a continuous composite lens unit.

2. A method of forming a lens unit which comprises melting a body of glass, molding under pressure from said body a central, substantially fiat glass blank, forming opposite section-receiving edges on said blank at right angles to the opposite faces thereof, molding under pressurea body of molten glass into two substantially fiat sections integrally connected by a, relatively nar- 5 lens unit.

angles to its fiat faces to fit in edge-to-edge relation on said section-receiving edges, and fusing the section-receiving edges to the edges of the lens sections to form a continuous composite PERRY JOHNSTON. 

